A. Field of the Invention
The present invention relates to golf clubs used in the game of golf. More particularly, the invention relates to an improved putter having a head construction which assists a golfer swinging the putter to impact a ball, in aligning the impact vector of the club head with a hole and maintaining the club head face perpendicular to the impact vector.
B. Description of Background Art
A number of prior art references disclose golf putters in which the head of the putter has structural elements that direct the eye towards the "sweet-spot" on the face of the putter. The "sweet-spot" is a relatively small area on the face of a club which overlies the center of percussion of the club head, i.e., that location at which a golf ball may be impacted without producing a torque about the hosel and shaft of the club.
Other prior art references disclose golf putter heads in which the heel and toe portions of the head are heavier than the center portion, to thereby increase the polar moment of inertia of the head over that of a head with uniform heel-to-toe weight distribution. A large polar moment of inertia is desirable because it resists any tendency of a golfer to twist the club shaft as it is swung forward to impact a ball, thus helping to insure that the club face will impact the ball squarely rather than obliquely. This in turn insures that the momentum vector imparted to the ball upon impact does not angle away from the impact momentum vector of the club head, which corresponds to an intended initial ball trajectory chosen by the golfer. Some prior art references disclose putter heads having a construction which incorporates both sweet-spot targeting visual features as well as heel and toe biased weighting.
References known by the present inventor to incorporate either or both characteristics discussed above include the following U.S. patents.
Winter, U.S. Pat. No. 3,921,984, Nov. 25, 1975, Clubhead Having Alignment Means And High Moment of Inertia Spaced From Center Of Gravity Thereof
Discloses a putter head with a rear portion angled obliquely outwardly and rearwardly to concentrate mass of the club head at higher radial distances from the geometric center/center of gravity of the head, to thereby increase the polar moment inertia from that of a head having a uniform transverse section. The obliquely angled rear surfaces protrude beyond the rear face of the club as a pair of symmetric fins resembling a bat-wing aircraft, and the head includes a center fin which protrudes perpendicularly rearwardly with respect to the front impacting face of the club, and forms with the wings in plan view an arrow-shaped structure pointed at the sweet-spot on the front face of the head, to facilitate alignment of the sweet-spot with the intended direction of travel of the ball.
Nelson, U.S. Pat. No. 5,127,653, Jul. 7, 1992, Golf Putter
Discloses a golf putter having a head with opposite heel and toe sections which are divergent rearwardly to draw the golfer's visual alignment to the sweet-spot. A cavity centrally positioned at the rear of the face is configured to resemble a part of the surface of a golf ball to remove weight and provide an additional visual putting alignment guide. The putter has an offset hosel which is adjustably secured to the head at assembly so precise face balancing can be achieved before final permanent assembly of the components.
Montgomery, III, U.S. Pat. No. 5,167,414, Dec. 1, 1992, Golf Putter
Discloses a golf putter head which is cast in one piece and comprises a face plate including a striking surface adapted to strike a golf ball with a sole plate extending rearwardly from the face plate at the lower end having an arcuate lower surface which is designed to accommodate golfers of different heights, an upper weighting member, spaced above the sole plate also extends rearwardly of the face plate and is constructed so as to provide two rearwardly projecting wing members which define a V-shaped recess having a bight which is essentially perpendicular to the striking face of the face plate, and a line or score mark is defined on the weighting member which is essentially perpendicular to the striking surface of the face plate to aid the golfer in aligning the putt. The weight distribution between the sole plate and the upper weighting member is such as to impart overspin to a golf ball and thereby insure that the ball rolls when struck and does not slide nor skid over a green.
Kinoshita, U.S. Pat. No. 5,131,656, Jul. 21, 1992, Impulse Performance Putter
Discloses a golf putter head having one mass section located directly behind the golf ball impact point and two other mass sections used for heel-toe weighting of the putter head. Two high moment of inertia structures are used to rigidly connect the mass section located directly behind the impact point to the heel-toe weighting mass sections. The high moment of inertia structures ensure that maximum momentum transfer to the golf ball is realized from the momentum of the heel-toe mass sections at impact.
The prior art references listed above disclose golf putters in which the heads are constructed in a manner intended to assist a golfer in impacting a ball with the sweet-spot of the putter head face by means of visual alignment elements directed toward the sweet-spot, avoid twisting the club shaft during a swing by increasing the polar moment of inertia of the head, or both. However, the prior art known to the present inventor fails to solve the following two problems that are related to visual alignment and shaft twisting, respectively.
First, while prior art visual alignment aids may assist in impacting a ball with the sweet-spot of a club head face, there remains the equally if not more important problem of aligning the impact vector with a hole which may be many feet away. Furthermore, if a green is not absolutely level, the golfer may have to aim the ball impact vector at a point laterally displaced from the hole, so that the initial velocity vector of the impacted ball in combination with the roll characteristics of the green will result in a curved ball trajectory terminating at the hole. Therefore, it can be readily appreciated that merely impacting the ball with the sweetspot of the club head will not insure that the ball will go into the hole.
Second, with respect to shaft twisting, a putter head having a large polar moment of inertia will counter a tendency of the head to twist about an axis directed through the center of gravity of the head. Thus, this construction is effective for putters in which the axis of the shaft is aligned with the center of gravity, i.e., a face-balanced club. However, many golfers prefer a putter construction in which the hosel and shaft are laterally offset a substantial distance from the center of gravity of the putter head to locate the hosel near the heel of the head. With this construction, the longitudinal axis of the shaft typically intersects the horizontal mid-plane of the head at a location closer to the heel than the toe; therefore, the moment arm of the toe portion of the head about the shaft axis is greater than that of the heel portion. This weight offset can result in a torque tending to twist the toe rearward as the club is swung forward.
The present invention was conceived of to provide a putter construction which facilitates aiming the trajectory of an impacted ball in a desired direction, and which permits adjusting the relative magnitudes of the heel and toe weight moments about the shaft axis, to thereby control the magnitude and direction of torques tending to twist the putter shaft in the hand when the putter is swung.